This invention relates to ERRP (EGF-Receptor Related Protein) specific antibodies that could be used 1) to study the functional properties of ERRP and; 2) as a diagnostic and prognostic tool for malignancies.
Growth factors and hormones exert pleiotropic effects on cellular functions, including mitogenic stimulation and modulation of differentiation and metabolism (Ullrich et al., Cell 61:203–212 (1990); Aaronson, Science 254: 1146–1153 (1991)). In many cases, these actions are mediated by the interaction of growth factors with cell surface tyrosine kinase receptors (TKRs), which results in enhanced receptor catalytic activity and tyrosine phosphorylation of intracellular substrates (Ullrich et al., supra, Aaronson, supra). Knowledge of the nature of these second messenger systems is still scanty, although some molecules which associate and/or are tyrosine phosphorylated by TKRs have been identified. These include the γ isozyme of phospholipase C (PLC-7) (Margolis et al., Cell 57: 1101–1107 (1989); Meinsenhelder et al., Cell 57: 1109–1122 (1989); and Wahl et al., Mol. Cell. Biol. 9: 2934–2943 (1989)); the p21ras GTPase activating protein (GAP) (Molloy et al., Nature 342: 711–714 (1989); Kaplan et al., Cell 61:125–133 (1990); and Kazlauskas et al., Science 247: 1578–1581 (1990)); the raf serine-threonine kinase (Morrison et al., Proc. Natl. Acad. Sci. USA 85: 8855–8859 (1988); and Morrison et al. Cell 58: 649–657 (1989)); the p85 subunit of the phosphatidylinositol 3-kinase (PtdIns-3K) (Coughlin et al., Science 243: 1191–1194 (1989); Kazlauskas et al., Cell 58: 1121–1133 (1989); Varticovski et al., Nature 342: 699–702 (1989); Ruderman et al., Proc. Natl. Acad. Sci. USA 87: 1411–1415 (1990); Escobedo et al., Cell 65: 75–82 (1991); Skolnik et al., Cell 65: 83–90 (1991); and Otsu et al., Cell 65: 91–104 (1991)) and some cytoplasmic tyrosine kinases (Gould et al., Mol. Cell. Biol. 8: 3345–3356 (1988); and Kypta et al., Cell 62: 481–492 (1990)). These signaling molecules are thought to mediate at least in part the mitogenic effects of TKRs (Ullrich, et al. supra; Aaronson, supra).
However, the Epidermal growth factor (EGF) receptor (EGFR) does not appear to efficiently interact with known second messenger systems (Fazioli et al., Mol. Cell. Biol. 11: 2040–2048 (1991); and Segatto et al., Mol. Cell. Biol. 11: 3191–3202 (1991)). Thus, there is need to ascertain the mechanism by which the EGFR functions in mitogenesis, and a particular need to identify and characterize the substrate (if any) of the EGFR.
Errors which occur in the mitogenic signaling pathway, such as alterations in one or more elements of that pathway, are implicated in malignant transformation and cancer. It is believed that in at least some malignancies, interference with such abnormal mitogenic signal transduction could cause the cells to revert to normal phenotype.
In addition, reagents useful in identifying molecular components of the mitogenic signaling pathway find utility as tumor markers for therapeutic, diagnostic, and prognostic purposes. Furthermore, identification of how such components differ from normal components in malignant tissue would be of significant value in understanding and treating such malignancies.
EGFR, a 170 kDa transmembrane glycoprotein protein with intrinsic tyrosine kinase activity, which binds EGF family of peptides, plays an important role in controlling cell proliferation and differentiation as was shown by Ullrich et al. supra. The EGFR possesses three functional domains that include extracellular, transmembrane and cytoplasmic. Ligand binding to the extracellular domain of EGFR leads to dimerization and activation of the receptor's intrinsic tyrosine kinase, located in the cytoplasmic domain, triggering a complex array of enzymatic and biological events leading to cell proliferation and differentiation.
Members of the receptor tyrosine kinase family are frequently implicated in experimental models of epithelial cell neoplasia as well as in human cancers (Hunter et al., Ann. Rev. Biochem. 54: 897–930 (1985); Yarden et al., Ann. Rev. Biochem. 57: 443–487 (1987); Candena et al., FESEB J. 6: 2332–2337 (1992); Glenney, Biochim. Biophys. Acta 1134: 113–127 (1992); and Joensuu et al., N. Eng. J. Med. 344: 1052–1056 (2000)). There is increasing evidence to support the concept that the malignant behavior of some tumors is sustained by deregulated activation of certain growth factor receptors. Such deregulation could be either structural alterations of the receptor itself (Downward et al., Nature 307: 521–527 (1984); and Sefton, In: R A Bradshaw and S Prentis (eds.), Oncogenes and Growth Factors. Elsevier Biomedixal Press, Amsterdam (1987)) or to the establishment of an autocrine loop, whereby the cells produce growth factors that stimulate their own growth (Cutlitta et al., Nature 216: 825–826 (1985); Betsholtz et al., Cell 39: 447–457 (1984); and Sporn et al., Nature 313: 745–747 (1985)). The receptors with intrinsic tyrosine kinases are activated following binding of their growth factors. One of the best studied receptor signaling systems from this family is that controlled by the EGF-receptor (EGFR), whose expression and enzyme activity have been linked to a number of malignancies, including cancer of the colon (Culig et al., The Prostate 28: 392–405 (1996); Barnard et al., Gastroenterology 108: 564–580 (1995); Khasharyarsha et al., Cancer and Metastasis Rev. 12: 255–274 (1993); and Gullick, Br. Med. Bull. 47: 87–98 (1991)). EGFR and its ligand TGF-α, a structural and functional analogue of EGF, are overexpressed in preneoplastic and epithelial cells (Malecka-Panas et al., Hepato-Gastroenterology, 44: 435–440 (1997); Relan et al., Biochim. Biophys. Acta 1244: 368–376 (1995); Barnard et al., Gastroenterology 108: 564–580 (1995); and Khasharyarsha et al., Cancer and Metastasis Rev. 12: 255–274 (1993). Moreover, cell lines derived from adenocarcinomas of various gastrointestinal (GI) tissues, including the colon have been found to overexpress TGF-α and its receptor EGFR (Coffey et al., Cancer Res. 46: 1164–1169 (1986); Ohmura et al., Cancer Res. 50: 103–107 (1990); Yoshida et al., Int. J. Cancer 45: 131–135 (1990); Coffey et al., Cancer Res. 46: 1164–1169 (1986); Anzane et al., Cancer Res. 49: 2898–2904 (1989). Because of EGFR's role in the development of progression of many epithelial cancers, efforts are being made to utilize EGFR as a potential target for epithelial cancer therapy. Several approaches, including monoclonal antibodies to EGFR and pharmacological inhibitor(s) of EGFR tyrosine kinase have been utilized. However, the effectiveness of most of the therapeutic regimen has, thus far, been limited primarily because of toxicity and/or lack of specificity.